Stainless steel
In 1798, Louis Vauquelin presented chromium to the French Academy for the first time. This element would eventually become the key ingredient in a new type of steel. Scientists James Stoddart and Michael Faraday observed that chromium-iron alloys resisted oxidizing agents in the early 1800s. Pierre Berthier noted their resistance against acid attacks in 1821 and suggested using them for cutlery. The material contains at least 10.5% chromium by mass. This specific percentage allows the formation of a passive film on the surface. The film protects deeper layers from oxidation when exposed to oxygen. It can self-heal if scratched or disturbed. Adding molybdenum improves resistance to pitting corrosion. Nitrogen increases mechanical strength while enhancing corrosion resistance. Some grades contain up to 30% chromium to suit aggressive environments.
Harry Brearley worked at the Brown-Firth research laboratory in Sheffield, England during 1913. He sought a corrosion-resistant alloy specifically for gun barrels. His discovery resulted in a martensitic stainless steel later known as AISI type 420. The announcement appeared two years later in a January 1915 issue of The New York Times. Krupp engineers Benno Strauss and Eduard Maurer patented austenitic stainless steel on the 17th of October 1912. They called it Nirosta, which became known as 18/8 or AISI type 304. Christian Dantsizen and Frederick Becket industrialized ferritic stainless steel around 1912. Elwood Haynes applied for a US patent on martensitic stainless steel in 1912. The patent was not granted until 1919. Over 25,000 tons of stainless steel were manufactured annually in the United States by 1929. Ford Motor Company continued calling the alloy rustless steel in promotional materials as late as 1932.
Austenitic stainless steels make up about two-thirds of all production worldwide. These alloys possess a face-centered cubic crystal structure maintained by nickel, manganese, or nitrogen. Type 304 and Type 316 belong to the 300 series chromium-nickel group. Ferritic steels contain between 10.5% and 27% chromium with little or no nickel. They have a body-centered cubic crystal structure and are magnetic. Type 409 and Type 430 fall into this category. Martensitic steels feature a body-centered tetragonal crystal structure. They are hardenable by heat treating and cold working. Type 410 and Type 440C represent common grades in this family. Duplex steels combine austenite and ferrite in a mixed microstructure. Commercial alloys often maintain a 50:50 ratio though some vary from 40:60. Precipitation hardening steels develop properties through specific heat treatments. The 17-4 PH grade combines martensitic hardening with precipitation hardening for high strength.
Electric arc furnaces melt stainless steel scrap along with other ferrous alloys. Molten metal transfers into ladles before entering the argon oxygen decarburization process. This step removes carbon by converting it into carbon monoxide gas. Continuous casting solidifies molten metal into slabs typically measuring two inches thick. Hot rolling reduces slab thickness to produce coils about one-eighth inch thick. Cold finishing involves pickling in acid solutions to remove oxide scale. Sendzimir rolling mills then cold roll the material to desired thicknesses. World production figures show China, Japan, South Korea, Taiwan, India, the US, and Indonesia as large producers. Italy, Belgium, and Spain were notable within EU production figures. Canada and Mexico produced none according to available data. Russia reported little production during recent years. The International Stainless Steel Forum publishes these statistics annually. Manufacturing processes determine whether final products become sheets, bars, wire, or tubing.
Stainless steel appears in construction materials for large buildings and bridges. Pharmaceutical plants use its biological cleanability which exceeds copper and aluminum. Food processing facilities rely on its resistance to acids and bacteria. Chemical engineering environments utilize grades like Type 316 for sulfuric acid resistance up to 20% concentration at room temperature. Water treatment systems employ stainless steel for durability against chloride ions. Automobile exhaust pipes often contain ferritic stainless steels like Type 409. Surgical instruments benefit from the alloy's strength and corrosion resistance. Major appliances incorporate stainless steel for both aesthetics and longevity. Storage tanks hold chemicals and food products without degrading over time. Power plates operate solid oxide fuel cells at temperatures around 800 degrees Celsius. Concrete reinforcing bars increasingly use lean duplex grades for structural applications. Coastal works require super duplex alloys to withstand harsh marine environments.
Life cycle cost calculations compare acquisition costs against operating expenses over decades. An average carbon footprint of 2.90 kilograms of CO2 exists per kilogram of stainless steel produced. Emissions from raw materials account for 1.92 kilograms while electricity contributes 0.54 kilograms. Direct plant emissions add another 0.44 kilograms to the total. Stainless steel remains 100% recyclable throughout its existence. Average objects contain about 60% recycled material in their composition. Approximately 40% originates from end-of-life products while 60% comes from manufacturing processes. The per capita stock reaches 170 kilograms in more developed countries. Collection rates vary significantly by sector with building infrastructure achieving 92% recycling. Transportation sectors recycle 85% of their stainless steel content. Household appliances show a 70% collection rate for recycling purposes. Maintenance and repairs often offset higher initial acquisition costs over long project lifespans. Loss of service can induce hidden societal costs like queues and wasted fuel.
Inhaling fumes during welding creates probable increased risks of lung cancer according to extensive research. Cadmium oxides, nickel, and chromium contribute to carcinogenic properties found in these fumes. All types of welding fumes were classified as Group 1 carcinogens by Cancer Council Australia in 2017. Small amounts of nickel and chromium leach into highly acidic foods during cooking. New stainless steel cookware releases trace metals when exposed to strong acids. No connection between stainless steel cookware and cancer has been established despite these findings. Nickel compounds are listed as cancer-causing substances by the National Cancer Institute. Welders face elevated risks compared to other metal workers based on epidemiological studies. Safety protocols must address both airborne particulates and dietary exposure concerns. Proper ventilation systems reduce inhalation hazards in industrial settings. Testing confirms that acid concentration directly influences leaching rates from cookware surfaces.
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Common questions
What is the minimum chromium percentage required for stainless steel to form a protective film?
Stainless steel must contain at least 10.5% chromium by mass to form a passive film on its surface. This specific percentage allows the material to protect deeper layers from oxidation when exposed to oxygen.
When did Harry Brearley discover martensitic stainless steel and where was he working?
Harry Brearley worked at the Brown-Firth research laboratory in Sheffield, England during 1913 when he discovered corrosion-resistant alloy for gun barrels. His discovery resulted in a martensitic stainless steel later known as AISI type 420 with an announcement appearing two years later in a January 1915 issue of The New York Times.
Who patented austenitic stainless steel called Nirosta and what date was it registered?
Krupp engineers Benno Strauss and Eduard Maurer patented austenitic stainless steel on the 17th of October 1912. They called it Nirosta which became known as 18/8 or AISI type 304.
How much carbon dioxide is emitted per kilogram of stainless steel produced globally?
An average carbon footprint of 2.90 kilograms of CO2 exists per kilogram of stainless steel produced. Emissions from raw materials account for 1.92 kilograms while electricity contributes 0.54 kilograms and direct plant emissions add another 0.44 kilograms to the total.
What are the carcinogenic risks associated with welding fumes from stainless steel?
Inhaling fumes during welding creates probable increased risks of lung cancer according to extensive research involving cadmium oxides, nickel, and chromium. All types of welding fumes were classified as Group 1 carcinogens by Cancer Council Australia in 2017.